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Jacob is a Java library that lets Java applications communicate with Microsoft Windows 
DLLs or COM libraries. It does this through the use of a custom DLL that the Jacob 
Java classes communicate with via JNI.  The library and dll isolate the Java developer
from the underlying windows libraries so that the Java developer does not have to write
custom JNI code.  
<p>
Jacob is not used for creating ActiveX plugins or other modules that
live inside of Microsoft Windows applications. 
<hr>

<h2> The Jacob Packages </h2>
<p>
The JACOB jar contains two main packages: the <code>com.jacob.com.*</code>> package and 
the <code>com.jacob.activeX</code> package.  The <code>com.jacob.com.*</code> package contains classes 
map very closely to the com dispatch model with the <code>com.jacob.com.Dispatch</code>
acting as the primary communication class.  Dispatch operate as a function library with 
a set of static methods that map very closely to the C++ Dispatch APIs provided
to the COM layer.
<p><code>com.jacob.activex.ActiveXComponent</code> can be used in place of Dispatch
to provide a more object like API.  
The only exception to this guideline is that the <code>ActiveXComponent</code> class is always
used to make the initial connection to the target dll/COM component.


<hr>
<H2> Considerations when doing server side automation of office </h2>
<p>
Most office and many windows client type applications are not written to be used
in high volume or multi-threaded server environment. There is a 
<a href="http://support.microsoft.com/kb/257757/">
support note </a>
on the Microsoft web site that discusses some of the issues. 
<p>
<hr>
<H2> Determining the API of the target application </h2>
<p>
Section not yet written.
<p>
<hr>
<h2> The Jacob DLL </h2>
<p>
Jacob.jar relies on a DLL file that it loads off of the library path or classpath.  
This means that you must either copy the appropriate jacob dll into your path or 
use VM options to add directory holding jacob dll to the path.  Prior to 1.14M6, 
the jacob DLL name was always "jacob.dll".  This made it hard to verify jacob 
was loading the correct dll when multiple copies of jacob were installed on a 
single system.  It also was confusing on 64 bit systems where the 32 bit and 64 bit 
dlls have the same tames. 
Starting in 1.14M6, Jacob's library 
loader selects a dll with the appropriate name based on the jacob release and platform.
The dll naming convention is: <BR>
<code>jacob&lt;platform&gt;.&lt;version.&gt;.dll</code>  
<p>
<h3>Classloader issues</h3>
The code is written so that the jacob.dll is only loaded one time per classloader.
This works fine in the standard application but can cause problems if jacob.jar
is loaded from more than one class loader.  This can happen in the situation where multiple
jacob dependent web applications run in the same container like a web server or JWS runtime.
In the case of a web server, Jacob is normally put in the application specific WEB-INF/lib directory.
This is the "right" way to do it and works in most situations.  
But, if Jacob is put in the WEB-INF/lib directory of each application's war file for more than 
one application then a problem occurs.
In this situation, the web server uses a different classloader for each application.
This means that each application will attempt to load the jacob.dll and errors
are generated.  The only way around this at this time (1.11) is to put the jacob.jar
in the common/lib because that classloader is inherited by all of the applications
so the DLLs will only get loaded once.  This problem is described in SF 1645463 and 
should be fixed in some future release, fix method and time not yet determined.
<p>
<hr>
<h2>Microsoft Visual C++ library dependencies.</h2>
<p>
	Jacob 1.15 is build with VC++ 2005 statically linked into the DLL.  This
	removes the need for a separate msvcr80.dll installation.
</p>
<p>
	Jacob 1.13 is built with VC++ 2005 that creates a dependency on msvcr80.dll.  
	Windows XP and later seem to already include the necessary components.  
	NT/2000 and Server/2003 require that you download the Visual C 2005 redistributable 
	package, vcredist_x86.exe from the Microsoft web site. 
	Microsoft has a download available that supplies the necessary components.
	It is distributed as a redistributable package.
	</p>
<p>
If you see the following message then you probably don't have the right C++ libraries.
</p>
<pre>
Exception in thread "main" java.lang.UnsatisfiedLinkError: C:\apps\...\jacob.dll: This application has 
failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem 
</pre>	
<pre>
<A href="http://www.microsoft.com/downloads/details.aspx?familyid=200B2FD9-AE1A-4A14-984D-389C36F85647&displaylang=en">
Visual C redistributable installer SP1</A>
</pre>

<p></p>
<hr>
<h2>Jacob Command Line Settings</h2>
This library supports several different command line options:
<table border=1>
<tr><td colspan=3>
<h3>dll path location and dll name customization</h3>
</td></tr>
<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	<h4>java.library.path</h4>
	</td><td>
	Standard Java property used to add the location of the jacob dll to the JVM's library path.
	(Added 1.11)
	<p>
	Example: <code>-Djava.library.path=d:/jacob/release/x86</code> 
</td></tr>

<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	<h4>jacob.dll.name</h4>
	</td><td>
	Override the standard DLL name with a custom one.  This stops jacob from 
	using its 32bit/64bit detection and dll rendezvous logic.
	Sometimes used when
	Jacob is bundled with another application and the application wishes
	to tie the jacob dll version number to the application version number. 
	(Added 1.14M7)
	<p>
	Example: <code>-Djacob.dll.name=MyFunkyDllName.dll</code> 
</td></tr>

<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	<h4>jacob.dll.name.x86 & jacob.dll.name.x64</h4>
	</td><td>
	Override the standard 32 bit DLL name with custom ones. 
	Sometimes used when
	Jacob is bundled with another application and the application wishes
	to tie the jacob dll version number to the application version number.
	(Added 1.14M7)
	<p>
	Example to override 32 bit dll name: <code>-Djacob.dll.name.x86=MyFunkyDllName-32bit.dll</code> 
</td></tr>

<tr><td colspan=3>
<h3>Memory Management</h3>
</td></tr>
<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	<h4>com.jacob.autogc </h4>
	</td><td>
	Determines if automatic garbage collection is enabled.  This is the
	only way to free up objects created in event callbacks.  	Automatic garbage collection , 
	based on Java gc rules, garbage collection can be enabled via the 
	<code>com.java.autogc</code> command line option. 
	<em>This feature was added in release 1.9 is not fully debugged.  </em>
	<p>
	There are real reasons for managing the 
	lifetime of JacobObjects on a per thread basis.
	Jacob normally manages the the com/Java object lifetime as described in the
	<a href="JacobComLifetime.html">JacobComLifetime.html</a> document.  
	Some users have run into situations where they wish to try and let the Java 
	GC lifetime manage the lifetime of objects.  This seems to usually be tied
	to long running threads or to objects created as part of event callbacks.
	Code was added to let users try and let the JVM manage the object life cycles
	even though the <a href="JacobComLifetime.html">JacobComLifetime.html</a> document 
	says this is a bad idea. Added 1.9.
	<p>
	<p> 
	This value is cached at startup and cannot be changed on-the-fly via <code>System.setProperty();</code>
	<p>
	The default value is <em>false</em>
	<p>
	Example: <code>-Dcom.jacob.autogc=false</code>
	
	</td></tr>
	
<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	<h4>com.jacob.includeAllClassesInROT</h4>
	</td><td>
	Acts as master switch for  and &ltclass_name&gt.PutInROT.
	This property determines if the (experimental) PutInROT property is even
	checked.  It was added in version 1.15 because the property check in 
	PutInROT brok applets because they are not allowed to check system properties
	at run time.  com.jacob.includeAllClassesInROT is checked at class initialization
	which is allowed. 
	<p>The default value of this flag is <i>true</i> which matches all behavior 
	prior to 1.13 and the default behavior for 1.13 on</p>
	<p>Setting this flag to false causes Jacob to check the  and &lt;class_name&gt;.PutInROT
	property for every Jacob object that is created.</p>
</td></tr>
<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	<h4>&ltclass_name&gt.PutInROT</h4>
	</td><td>
	Lets a program specify that instances of certain classes are to not be inserted
	into the ROT.  This experimental (1.13) feature provides a mechanism for freeing
	VariantViaEvent objects that are created in Event threads.  There is normally no 
	way to free those objects because the thread terminates outside of any normally MTA/STA
	Startup/Teardown code.  Each event occurs in a new thread and creates a new ROT entry
	so they grow without bounds. 
	<p>
	This option may cause VM crashes in certain situations where windows memory is freed 
	outside of the thread it was created in but empirical evidence shows there are
	situations where this great reduces the long running memory footprint of applications
	that process a lot of events. <em>This function is still experimental</em>.
	The functionality was added 1.13. Some of this overlaps the experimental <code>com.jacob.autogc</code> introduced
	in 1.9.
	See the ROT.java test program for an example of the effects of this option.
	<p> 
	This value is checked every time and can be changed on-the-fly via <code>System.setProperty();</code>
	<p>	
	
	Example: <code>System.setProperty("com.jacob.com.VariantViaVariant.PutInROT","false");</code>
	<BR>
	Example: <code>-Dcom.jacob.com.VariantViaVariant.PutInROT=false</code>
</td></tr>
	
<tr><td colspan=3>
<h3>Debugging and Troubleshooting</h3>	
</td></tr>
<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	<h4>com.jacob.debug</h4>
	</td><td>
	Determines if debug output is enabled to standard out. 
	<p> 
	This value is cached at startup and cannot be changed on-the-fly via <code>System.setProperty();</code>
	<p>
	The default value is <strong>false</strong>
	<p>
	
	Example: <code>-Dcom.jacob.debug=false</code>
	</td><tr>
	
<tr><td>&nbsp;&nbsp;&nbsp;</td><td valign="top">
	
	<h4>-XCheck:jni</h4>
	</td><td>
	This turns on additional JVM checking for JNI issues.  This is
	not an actual JACOB system property but a property used by the JVM.
	<p>
	The default is "no additional checking"
	Example: <code>-XCheck:jni</code>
</td></tr>
</table>
	
<p></p>
<hr>
<h2>Finding the DLL version using windows command line</h2>
The jacob.dll file includes the jacob release number in the version field.  
Run the following from the command prompt <code>dumpbin /version jacob.dll</code> .
The dll version number is stored in the "image version" field of the 
"OPTIONAL HEADER VALUES" section. 
This information from <a href="http://msdn2.microsoft.com/en-gb/library/h88b7dc8(VS.71).aspx">
The Microsoft msdn web site</a>

<hr>
<h2>Unit Tests</h2>
Jacob must know the location of the DLL when running the unit tests in Eclipse.
The simplest way to do this is to add the dll path to the unit as a VM argument.
The argument should be specified based on where you installed the jacob source package. 
If you have jacob unpacked in c:/dev/jacob and built using build.xml, 
then the vm arguments would be: 
<br><code>-Djava.library.path=c:/dev/jacob/release/x86</code> .

<p>
Last Modified 4/2008 1.15

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